I was at my local park the other day, watching my sons playing tennis, and spotted the Mayor of London on another court - blond hair flying, Hawaiian shorts a go-go. It was quite exciting. I even toyed with the idea of capturing the Boris serve on camera and posting it on Twitter, but just as quickly dismissed it. Let the man play an undisturbed game of tennis.

But the temptation is now there, all the time. Your smartphone is capable of instant, global dissemination of whatever image you choose to capture - be it Boris looking dishevelled or, as we have just seen, a thin-looking Sarah Ferguson out and about in New York.

In days gone by, famous people were only accosted in what one might call red-carpet mode, or at least when they had just had a visit from hair and make-up. Nowadays a celeb, any celeb, at any time of day or night, anywhere, is a business opportunity for the brave smartphone-owner. Even in New York or London, cities which used to be cool with the famous.

Enough is now enough for Alec Baldwin. The irascible but brilliant actor, in a spirited rant for New York Magazine, has announced that he is so utterly fed up with being snapped all the time by people wielding mobile phones, that he is quitting New York for LA, where he thinks he can more effectively reduce his contact with the public.

What cheek, some people will think. Have not we, the public, allowed Mr Baldwin an enviable lifestyle, and a colossal bank balance? Of course. But the average snapper, he suggests, is not out to have a souvenir. They want to see the worst of him, and sell it, and after the “gay slur” controversy that dogged Baldwin last year, he is presumably seen as fair game.

These days, we hunger for images of famous people behaving badly. “I loathe and despise the media in a way I did not think possible,” continues Baldwin, who points out, inter alia, that he has given over $15m to charity. He also uses his piece to defiantly defend himself from accusations that he is a homophobe. “Anything good you do is tossed in a pit, and you are measured by who you are on your worst day,” he writes.

Just looking at those recent pictures of Fergie - gaunt in the unforgiving sunshine, no make-up, smiling awkwardly - and I know what Baldwin is referring to. It doesn’t reflect well on us, the wielders of the cameras.